Work machines such as agricultural tractors, combines, construction and forestry equipment continually rely to a greater extent upon electronics and electronic controls. Work machines may operate in extreme environments compared to other applications. Among other concerns, it is necessary for on-board electronics to be designed from an electronics packaging standpoint with vibration, heat transfer and electromagnetic interference (EMI) in mind. Thus, electronics for work machines must be generally of a robust design.
When designing electronic modules that are to be embedded in an application such as a tractor or construction vehicle, it is critical that the mechanical packaging concept (the enclosure holding the electronic circuit boards) is sealed against possible exposure to the elements and designed to withstand high levels of vibration. For example, an electronic module mounted on the arm of a backhoe or trencher may be completely submersed in water for periods of time as the operator digs into swampy ground. Failure points for electronics modules in these situations include the seam between enclosure halves and any opening in the enclosure, such as the location where a cable exits the enclosure to connect to an external module. These potential trouble spots must be thoroughly sealed against the intrusion of moisture and dust. In addition, when a cable enters the module, it must be connected at some point to the printed circuit board inside the enclosure. This point of connection can be a potential failure point if the module is subjected to high levels of vibration and mechanical shock.
There are industry standard methods for addressing these potential failure points. To seal two halves of an enclosure against the environment, designers may use a pre-formed gasket (of silicone or similar material) sandwiched between the halves to prevent intrusion. Other methods include dispensing a bead of wet sealing material around the lip of one or both of the enclosure halves and pressing them together to form a seal. Although these same gasketing methods can be used around the opening where a cable exits the enclosure, it is more difficult to create a seal between the dislike materials of the enclosure and the cable. A technique called overmolding, in which a plastic or similar material is molded around wires to create a kind of protective shell can be used to create a cable that has a built in seal molded around it. This is a separate and additional process that must be used in addition to the gasket placed between the enclosure halves.
To address the issue of connecting a cable to a printed circuit board, it is often best to insert the incoming wires directly into preformed holes in the circuit board, and solder each independently, rather than try to use a connector that may vibrate the board during use. Unfortunately, this practice often requires hand placement of the individual wires in the holes, which is subject to error, and hand soldering. These manual practices are labor intensive and increase the cost of the module.
What is needed in the art is an electronic module which is easier and faster to assemble, and has less chance for assembly errors.